The invention relates generally to an integrated thin-film lateral multi-junction solar device. The invention relates further to a related method of building an integrated thin-film lateral multi-junction solar device.
Solar cells are photovoltaic devices which convert sunlight into electricity. Solar cells are either made of crystalline silicon wafers or are based on thin-film silicon technologies. Alternatively, solar cells may be based on amorphous silicon. Other alternatives may be based on CIGS (Copper-Indium-Gallium-(Di-(Selenide)), CdTe (Cadmium-Telluride) or CZTS (Copper-Zinc-Tin-Sulfide). Solar cells are used in a wide range of applications. They may, for example, be used to deliver power into a public power grid, recharge batteries in remote locations, recharge mobile devices like mobile telephones, or may function as a sole energy source for pocket calculators. One key design parameter for solar cells is the production price in relation to the efficiency of the conversion process from light energy to electrical energy.
In order to maximize the energy yield from photovoltaic conversion, the highest efficiencies are reached by multi-junction solar cells, and reaching efficiencies over 45% so far. In order to simplify the required optimization of optical and electrical properties, lateral multi-junction solar cells are a means to separate the radiation spectrum into spectrum bands most suitable for a material system with a band-gap optimized for a spectrum band. Lateral multi-junction solar cells have a series of individual solar cells placed side by side on a substrate, each solar cell with differing characteristics such as material composition, band-gaps, absorption and diode characteristics. In the standard configuration, individual sub-cells are connected in series, reducing the overall efficiency with the worst performing diode characteristics. This is a major drawback to traditional multi-junction solar cells.